The amino terminal domains of sheep Cx46 or Cx50 determine their gap junction channel open stability and unitary channel conductance

Benny Yue, The University of Western Ontario

Abstract

Connexins form intercellular communication channels known as gap junctions (GJs), which are found throughout the vertebrate species. GJs formed by different connexins harbor unique channel properties that have not been fully defined. High-resolution structures of native Cx46 and Cx50 GJs from sheep (sCx46 and sCx50) were recently resolved. Molecular dynamics studies identified the NT domains, especially the 9^th position, as key determinants in the differences of energetic barrier to K⁺ permeation in sCx46 and sCx50 GJs. We studied functional properties of GJs formed by sCx46, sCx50, NT domain swapped chimeras (sCx46-50NT and sCx50-46NT), and point variants at the 9^th residue (sCx46-R9N and sCx50-N9R) in GJ-deficient N2A cells. We found that these variants formed functional GJs except sCx46-50NT. Altered single channel conductance, open dwell time, and V_j-gating in these variants indicate that that the NT-domain is important for the rate of ion permeation, open stability, and V_j-gating of these GJs.